1. Field of the Invention
This invention relates generally to doctors used in papermaking machines, and is concerned in particular with the provision of a blade holder which is readily separable from the doctor back and removable from the papermaking machine for cleaning, inspection and repair.
2. Description of the Prior Art
The main components of a doctor system include the doctor blade, the blade holder, the doctor back and the loading mechanism. The doctor blade keeps the roll clean and/or sheds the sheet. It must be perfectly flat, straight and parallel, and its composition must be compatible with the roll to be doctored.
The blade holder exerts a uniform, designated load pressure on the blade. It holds the blade firmly against the roll, accommodates roll irregularities and, within limits, compensates for thermal expansion.
The doctor back is in essence the backbone of the doctor. It serves as the support structure for the blade holder. The loading mechanism pivots the doctor back to load the doctor blade against the roll.
Doctor blade holder designs used in recent years are more complex and have more components than the simpler blade holders used in the past. As a result, the more recent holder designs require more routine cleaning and maintenance. The doctor blade holders are normally mounted to the doctor back rigidly with a series of fasteners. Maintenance and cleaning of the blade holder can take place while the doctor remains in the machine but only in installations where the holder is accessible. However, in many cases, papermachine framework or other equipment prevents access to the blade holder while it is in the papermachine. In these cases, the complete doctor structure including the doctor back and attached holder must be removed from the papermachine to perform any cleaning or maintenance work. This task involves removing heavy equipment which requires extensive manpower and machine downtime. After making the necessary repairs, the entire doctor assembly must be re-installed in the papermachine, consuming more valuable manpower and time. In addition to the re-installation, the doctor must be re-aligned to the roll surface for optimum doctor performance.